Exposure meter



June 1940- H. SCHWARTZMANN 2,205,312

EXPOSURE METER Filed July 25, 1939 INVENTOR HARRY SCHWARTZ/MANN ATTORNEY5 Patented June 1 8, 1940 UNITED STATES PATENT OFFICE nxroscar METERApplication July 25, 1939, Serial No. 286,333

6 Claims.

My invention relates generally to photographic exposure meters, andspecifically to photographic exposure meters of the extinction type. Themain object of my invention is the provision of a device of thecharacter described whereby the different variables-shutter speed, lensapertures, or combinations thereof-can be determined in relation to theknown existing constantsfilm emulsion sensitivity, light conditions, orany thereof.

The object of my invention is to provide a simple device whereby, forall kinds of photography as well as cinematography, the shutter speedand lens openings for a particular film and under certain light andaction conditions can be determined easily and quickly.

A further object of my invention is the provision of an exposure meterwhich comprises a pluralityof concentrically mounted circular discs.

A further object of my invention is the provision of an exposure meterwhich comprises a plurality of concentrically-mounted, circular discs ofdifferent sizes, certain of which discs bear indicia related to indiciaon others thereof.

A further object of my invention is the provision of an exposure meterwhichcomprises a plurality of concentrically mounted, circular discs,adapted to rotate. independently of one another, certain discs beingalso adapted to ro tate simultaneously with others thereof.

A further object of my invention is the probision of an exposure meterwhich comprises a plurality of circular discs, concentrically androtatably mounted, certain of which discs are transparent and certain ofwhich discs are opaque.

Other and still further objects of my invention will be apparent andwill be pointed out hereinbelow in the specification of illustrativeembodimerits.

In the drawing annexed hereto, forming a part hereof:

Figure 1 is an exploded perspective view of the component parts of oneform of device con- 45 structed according to and embodying my invention;

Fig. 2 is a top plan view of the assembled device;

Fig. 3 is a bottom plan view thereof; 60 Fig. 4 is a section on the line44 of Figure 2; and

Hg. 5 is a view similar to Figure 4 of a modification,

Reference numeral ill indicates my new and I improved exposure metergenerally, which comprises four circular discs, concentrically mountedone above the other.

Topmost disc I 2 is centrally apertured, as at l4, and is provided witha projecting tab l6 whereby the disc can be rotated about its axis. DiscI2 is stamped or otherwise formed of relatively thin opaque material,such as laminated acetate, or any suitable metallic material, etc., andhas stamped or cut out therefrom an arcuate, semi-circular window l8,near the periphery thereof. The window I8 begins opposite tab it andextends clockwise around the disc to the diametrically opposite sidethereof. On the underside of this topmost disc l2, a strip of film 20 issecured, which is visible through window i8. That portion 22 of strip 20which can be viewed through window I8, is of graduated density. Portion22 is perfectly transparent at the beginning thereof near tab 16, andprogressively less so until it is substantially opaque or nearly so atthe opposite end 24. If desired, tab l6 may be provided with a suitableaperture 26, for purposes to be explained below.

The second disc 40 is also circular, and centrally apertured, and isprovided similarly with a a projecting tab 42 so that the disc can berotated about its axis. Disc 40 is of greater diameter than disc l2 anda peripheral platform portion 44 thereof projects beyond disc l2 whenthe two are superimposed. Disc 40 is formed of a transparent material.On platform 44, I place the information anent film emulsion sensitivity,lens apertures, and the filter factors. The lens aperture indicia 46 areinserted ranging from 1.4 to in a clockwise direction starting adjacenttab 42. The film emulsion sensitivity ratings 48 (American Sheinerdegrees are used for illustration only, and not for limitation) areinserted, also in clockwise direction, starting from "14" after the lastlens indicia 45" and increasing to 32 near the first lens indicia 1.4.The filter factors 50 are inserted among the sensitivity ratings 48, ina counter-clockwise direction. For convenience in use, the film ratings48 and lens openings 46 may be in different 5 color, and the filterfactors 50 are in a different and distinctive type.

The third disc is also circular, and centrally apertured. Disc 60 ispreferably opaque, and has formed therein, as by stamping or otherwise,a semi-circular, arcuate window 62. Disc 60 is of greater diameter thandiscs l2 and 40, and has an annular platform portion 64 which projectsout beyond the disc 40 when in superposed relation. Window 62 is solocated that when the discs are all assembled, window I8 on disc I2coincides with window 62 in disc 60. Shutter speed indicia 66 are placedon platform 64, ranging from one one-thousandth (M sec.) of a second upto one hundred and twenty (secs) seconds in a blockwise direction. Onthe underside of disc 60, as in Fig. 3, I insert indicia 60 to indicategeneral light conditions, ranging in a clockwise direction, from indoorsthrough cloudy, sunshine and snow and seascape. The first of theseindicia 68 are placed opposite one end I0 of window 62.

A fourth disc is also provided, centrally apertured at 82, and having aprojecting tab 84 formed thereon. Disc 80 may be formed, as by stampingor otherwise, of an opaque material. A circular opening 85 is formed inthe body of disc 80, in line with tab 84 (See Figs. 1 and 3). Aperture06 is of diameter substantially equal to or just a bit greater than thewidth of windows I8 and 02, in discs I2 and 60 respectively, and is solocated with respect to the center of the disc, that when the discs areconcentrically mounted, one on top of the other, aperture 06 will lineup with said windows I8 and 62 (see Fi 4).

I preferably assemble the discs in the following manner: Disc I2 issuperposed on disc 40 and the two secured by a centrally inserted eyelet90. By means of this connection, disc I2 may be rotated independently ondisc 40, but when disc 40 is rotated, it carries with it the smallerdisc I2. The pre-secured discs are then placed on top of discs 60 and 80and the four concentrically secured by a second and larger eyelet 92.The lower discs 60 and 80 may thus be independently rotated with respectto each other and with respect to the upper discs I2 and 40.

In operation, the correct film sensitivity being used is firstdetermined, and disc I2 rotated with respect to disc 40 by means of tabI6 so that the correspondingly correct Sheiner number appearing onplatform 44 of disc 40 may be viewed through window 26. The rearmostdisc 80 is then rotated by tab 84, so that the tab points to or overliesthe corresponding general light condition of indicia 68 on the undersideof the third disc 60, and at the periphery thereof. The device I0 isthen brought to the eye of the user and presented face outwardly towardthe object being photographed. The subject through the aperture 86, anddisc 40 rotated by means of tab 42 projecting beyond the periphery ofdisc 60 (and carrying with it disc I2) until the details of the subjectcan barely be distinguished. Referring to Fig. 2, it will be readilyappreciated that any rotation of disc 40 with respect to disc 60 causesa relative movement of lens aperture indicia 46 with respect to shutterspeed indicia 66. Thus, as shown in Fig. 2, the lens aperture 3.5 willbe suitable for an exposure at a shutter speed of one-tenth of a second.

When filters are used, the exposures must be increased to compensate forthe loss of light through the various filters. To adjust my device forany filter, the normal reading is first taken and the position of thesmall 0 99 on platform 44 of disc 40 is noted in relation to the timeshutter speed scale I56. Disc 40 is then rotated until the proper filterfactor 50 is brought to the same position where the o 99 was originally,providing an automatic compensation by time increase for the filterbeing used.

My device may also be used for cinematography since I provide on theprojecting platform poris thenviewed tion of disc 60 the frames persecond indicia used for motion picture cameras.

In the modified form of my device illustrated in Fig. 5, the discs andtheir relative disposition are identical with my preferred embodiment,ex-' cept that discs I2 and 40, and discs 60 and 80 are first secured inpairs by means of individual eyelets I00 and I02 respectively and thensecured together by means of a large eyelet I04. If desired, and inorder to bring the discs closer together, eyelets I00 and I02 may becountersunk to some extent, as seen at I05, I01. This method ofsecurement will prevent any slippage once the appropriate settings ofdiscs I2 and 80 have been made with respect to discs 40 and 00respectively.

I claim: 1

1. A device of the character described comprising a plurality of discssuperposed one above the other, and means to rotatably secure the discstogether in such relation, the topmost of said discs .having thereon astrip of graduated density, another of said discs constructed to permitthe passage of light therethrough disposed below' the first disc havinga plurality of scales thereon, one of said scales defining filmsensitivity ratings, the first referred-to disc having an index thereonadapted to cooperate with the film sensitivity rating scale on thesecond referred-to disc, a third disc below the first two having aplurality of scales thereon defining shutter speeds and general lightconditions, and a fourth disc, below the first three, having an indexthereon cooperating with one of the scales on the third disc and havinga relatively small circular viewing opening therein corresponding insize to the width of the density strip, said third disc having anopening therein through which the graduated density strip of the firstdisc can be viewed through the opening in the fourth disc.

2. A device as in claim 1 in which the first disc is of opaque materialexcept for the graduated strip, the second disc is of transparentmaterial, and the third and fourth discs are of opaque material exceptfor the openings therein.

3. A device as in claim 1 in which the first disc is of apaque materialand has an arcuate window therein inwhich the graduated density strip ismounted, the second disc is of transparent material; the third is ofopaque material and has an arcuate window therein which coincides insize and shape and position to the arcuate window in the first disc, andthe various discs are so mounted that upon relative rotation thereof,the various discs openings may be placed in registry.

4. A device of the character described comprising a plurality ofcircular discs superposed one above the other, and means to rotatablysecure the discs together in such relation, the topmost of said discshaving thereon a strip of graduated density, another of said discsconstructed to permit the passage of light therethrough disposed belowthe first disc and of greater diameter than said first disc having aplurality of scales thereon on the portion thereof which projects outbeyond the margins of the topmost disc, one of said scales definingfilpi sensitivity ratings, the first referred-to disc having an indexthereon adapted to cooperate with the film sensitivity rating scale onthe second referred-to disc, a third disc below the first two and ofgreater diameter than the second disc having a plurality of scalesthereon defining shutter speeds and general light conditions, and afourth disc, below the first three,

having an index thereon cooperating with one of the scales on the thirddisc and having a relatively small generally circular viewing openingtherein corresponding in size to the width of the density strip, saidthird disc having an opening therein through which the graduated densitystrip of the first disc can be viewed through the opening in the fourthdisc.

5. A device as in claim 4 in which the shutter 10 speed scale on thethird disc is on one side thereof and the general light condition scaleis on the reverse side thereof.

6. A device as in claim 4 having means to rotatably secure all fourdiscs together in superposed relation and having the top two discs andthe bottom discs secured in pairs by means of individual eyelets wherebythe bottom two discs may be rotated as a unit relative to the top twodiscs as a unit.

HARRY l0

